The U.S. Transportation Security Administration has acknowledged that a passenger bound for Tokyo passed through security in Atlanta with an undetected gun.

News outlets cite an agency statement saying the passenger passed through "a standard screening TSA checkpoint with a firearm" at Atlanta's Hartsfield-Jackson International Airport on Jan. 2. The passenger notified Delta Airlines officials after landing at Tokyo's Narita International Airport.

The TSA says standard procedures were not followed during the screening, but further details weren't released. The agency says it "will hold those responsible appropriately accountable."

The screening took place amid the ongoing partial federal government shutdown during which TSA workers aren't being paid. But the agency says the checkpoint was fully staffed at the time, with the rate of unscheduled absences the same as a year ago.